Hepatitis C is a viral hepatitis caused by infection with hepatitis C virus (HCV). In Japan, the number of patients suffering from HCV infection is about 2,000,000, and progression to chronic hepatitis occurs in 60 to 80% of HCV patients. In cases where treatment is not carried out and chronic hepatitis is maintained for 10 to 30 years, progression to liver cirrhosis/liver cancer occurs in 30 to 40% of patients. Examples of antiviral therapies for removal of HCV include interferon therapy, whose treatment results have been improved by the combined use of ribavirin and the pegylation of interferon.
As a result of analysis of about 900,000 sites in human genes, which are said to be different among individuals, in 314 Japanese patients for whom the pegylated interferon+ribavirin combination therapy is effective or ineffective, it has been reported that SNPs existing in the gene for IL28B, which is an interferon (IFN), and in the vicinity of the gene are involved in the therapeutic effect (Nature Genetics 41, 1105-1109 (2009)). Further, it has been reported that out of the 6 SNPs that were predicted to be involved in the effect of the pegylated interferon+ribavirin combination therapy, the SNP identified as rs8099917 has the largest influence on the therapeutic effect (PLoS One. 2010 Oct. 29; 5(10):e13771).
Ribavirin-induced anemia is a major factor that forces anti-hepatitis C virus (HCV) therapy to be terminated or reduced (Hepatol Res. 2010 November; 40(11):1063-1071). As a result of the evaluation of the clinical significance of ITPA gene variations in Japanese hepatitis C patients treated with the pegylated interferon (PEG-IFN)/ribavirin combination therapy, it has been reported that rs1127354, which is a functional SNP in an ITPA exon, is a useful predictive factor for ribavirin-induced anemia (Gastroenterology. 2010 October; 139(4):1190-7. Epub 2010 Jul. 14).
PLoS One. 2010 Oct. 29; 5(10): e13771 reports that mutation at IL28B (rs8099917) is strongly involved in the effect of the pegylated interferon/ribavirin combination therapy in hepatitis C patients, and detection of the presence/absence of a mutation at IL28B (rs8099917) was carried out by sequence analysis. HePATOLOGY, Vol. 53, Issue 2, pages 415-421, 2011 reports that mutation at ITPA (rs1127354) is strongly involved in anemia during treatment with the pegylated interferon/ribavirin combination therapy, and detection of the presence/absence of a mutation at ITPA (rs1127354) was carried out by sequence analysis.
However, it is very laborious and costly to carry out genomic DNA extraction from whole blood at actual clinical sites for investigating SNP variation in hepatitis C patients as described in PLoS One. 2010 Oct. 29; 5(10): e13771 and HePATOLOGY, Vol. 000, No. 000, 2011. Therefore, it is assumed that the demand for a technology with which the presence/absence of mutations can be automatically and directly assayed using whole blood will increase. Further, because of the involvement of IL28B (rs8099917) and ITPA (rs1127354) in the effect of the pegylated interferon/ribavirin combination therapy, it is highly likely that a technology that allows the simultaneous assay of the presence/absence of mutations in IL28B (rs8099917) and ITPA (rs1127354) will be required in the future in the clinical field, but such simultaneous detection cannot be done by either PLoS One. 2010 Oct. 29; 5(10): e13771 or HePATOLOGY, Vol. 000, No. 000, 2011, since detection of the presence/absence of mutations in IL28B (rs8099917) and ITPA (rs1127354) was carried out by sequence analysis.
JP 2002-119291 A describes a method wherein a nucleic acid probe labeled with a fluorescent dye is hybridized with a target nucleic acid and the amount of decrease in the luminescence from the fluorescent dye is measured. However, in cases where a nucleic acid probe labeled with a fluorescent dye is hybridized with a target nucleic acid and the amount of decrease in the luminescence from the fluorescent dye is measured, the sequence of the nucleic acid probe cannot be arbitrary and an appropriate sequence must be found for each mutation.